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Monetary Cost of an EMI Test Failure

Successful Projects Prevent Electromagnetic Interference.

Anyone who has been involved in electromagnetic interference testing is aware – sometimes painfully aware – that EMI tests can be expensive. If a product fails an EMI test, costs quickly escalate.

Recently, a customer shared with us what it cost them to fix a relatively simple EMI problem. Shortly after they recovered, they purchased a license for EMI Analyst™. Their engineering manager confided, “If we had used EMI Analyst™ during product design, we could have prevented this problem, and the software would have already paid for itself.”

Almost all EMI problems are preventable

Our customer, Aviation Controls Company (not their real name), is a well-known company that designs and manufactures electronics for the commercial aircraft industry. ACC was under contract to develop a new cabin lighting system. It was a project similar to past successful designs they have done. The EMI requirements were slightly tougher, but ACC has experienced designers and expected to sail through EMI qualification with no surprises.

On the fourth day of EMI testing, their electronic controller failed a test. During RF Conducted Susceptibility, the equipment under test started to behave erratically and then shut down.

The test operator stopped the test, went back, and repeated. Sure enough, the problem occurred again. No smoke, no damage, but the unit was clearly susceptible to the injected noise.

Now, what? Testing was halted until the cause was known and the issue was fixed.

Sometimes you get lucky

Fortunately, it took ACC’s engineer and technician just two days at the lab to isolate the problem, formulate a fix, and retrofit the hardware to prove they had a solution.

At first glance, two days does not sound too bad. The lab runs about $2000 per day, and the cause of the test failure was not too difficult to figure out. In the big scheme of things, two days is not a big deal.

Laboratory costs are only the beginning

EMI tests must be performed on production-equivalent hardware. Before formal testing could resume, there was a lot of work to be done.

EMI qualification testing is one of the last hurdles before a product is delivered to the end customer or is put on the market. By the time a product reaches EMI testing it has been thoroughly analyzed and validated, it has to pass a litany of environmental tests, and all of its drawings have been released.

Change is never easy

To fix their conducted susceptibility problem, ACC had to add filter components to a few susceptible signal lines, but there was no room on the circuit boards for the additional filter components. By the time it was done, this “simple” design change required:

– New board layout, fabrication, and assembly. Old boards were scrapped.
– Production parts selection and procurement
– Design margin assessment
– Thermal, vibration, and reliability analyses
– Drawing changes and release cycle
– Customer status updates
– Acceptance Test Procedure
– Quality Assurance witnessing and approval

The cost of this one test failure is more than $25,000

ACC estimates it took more than 200 man-hours to implement the design change.

At a burden rate1 of $125 per hour, the design change cost ACC about $25,000.

And that doesn’t include EMI lab charges incurred while troubleshooting or the time it took to repeat the failed test, which adds another $6000 to the bill.

Prevention is cost-effective

After this painful lesson, ACC decided to invest in up-front EMI analysis, giving EMI the same level of attention they give other design disciplines.

For more information about EMI Analyst™ please see the product pages at http://www.emisoftware.com.

1 Burden rate is what it costs a company for each employee. It includes not just salary, but support staff, facility costs, benefits, and equipment costs. For most high-tech companies in the US, burden rates are between $125 and $175 per hour.

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